Your quilt is beautiful! I want to make one like it.
I do like Yvonne does. But I have a BIG table made just for cutting fabric & pinning borders on. I lay my top out on the table, put my border face down on it & pin A LOT! I trim off the end of the border. And my borders are always cut on the width of the fabric. No problems.
We do longarm quilting & get a lot of friendly(wavy) borders. We try to give advice & information, even have the ladies over to show them how I do them. Then, we do our best with the ones we get. LOL
Linda